A conventional beverage extracting apparatus for vending machines is shown in FIGS. 1 and 2 (Japanese Patent Publication SHO 62-182897). A liquid mixture of water and the beverage raw material, for example a powder, is introduced into cylindrical mixing chamber 1 through inflow port 1a. Before valve 2 opens the inflow port 1a, bottom opening 1b is closed as a segment of a rolled filter sheet 4 is raised by filter support 5. Filter support 5 is urged downwardly by return spring 5a which also provides for the opening and closing of bottom opening 1b. After the liquid mixture is stored in mixing chamber 1, valve 2 is closed and pressurized air is supplied into the cylinder from pressurized air generating means to agitate the mixture. Liquid mixture stored in mixing chamber 1 is forcibly filtrated and extracted by the pressurized air through filter 4.
A conventional filter support drive mechanism 6 is constructed, for example, as shown in FIG. 2. Cam 6b is rotated by motor 6a causing transmitting mechanism 6c to move downwardly. Lever 6e pivotably supported at position 6f is rotated between the positions illustrated by the continuous line and the dashed line in FIG. 2 by engaging the bottom portion of transmitting mechanism 6c with one end of lever 6e. The other end of lever 6e engages lifting frame 6d attached to filter support 5. When lever 6e is rotated clockwise from the position shown by the continuous line to the position shown by the dashed line, filter support 5 is raised with lifting frame 6d. Consequently, the bottom opening 1b is closed by filter support 5 and filter 4 as shown in FIG. 1.
After the liquid mixture stored in cylinder 1 is forcibly filtrated and extracted through filter 4, valve 2 opens inflow port 1a, and the bottom opening 1b is again opened. If bottom opening 1b is opened before valve 2 opens inflow port 1a, then the spent grounds left on filter 4 and the liquid mixture left in cylinder 1 are exhausted by the high pressure in cylinder 1 to the inside of the vending machine.
However, in the construction of the above beverage extracting mechanism, the opening of inflow port 1a is formed relatively large to introduce the hot water and the raw material of the beverage into cylinder 1 as quickly as possible. Accordingly, the diameter of valve 2 is large to accommodate the large flow rate through inflow port 1a. Consequently, valve 2 receives a large biasing pressure due to the high pressure in cylinder 1. As a result, it is necessary for a large driving force to be added to valve 2 to open inflow port 1a. Therefore, a large valve driving mechanism is needed. In addition, when valve 2 opens inflow port 1a, hot water on the surface of valve 2 exhausts through inflow port 1a with the possibility of hot water contaminating and clogging outlet of a conduit for introducing the raw material.